Objectinfo json: write incrementally and in numeric order

This script was used on test data:

----------
#!/usr/bin/env python3
import json
import sys
import re

def json_dumps(data):
    return json.dumps(data, ensure_ascii=False,
                      indent=2, separators=(',', ': '))

for filename in sys.argv[1:]:
    with open(filename, 'r') as f:
        data = json.loads(f.read())
    if 'objectinfo' not in data:
        continue
    trailer = None
    to_sort = []
    for k, v in data['objectinfo'].items():
        if k == 'trailer':
            trailer = v
        else:
            m = re.match(r'^(\d+) \d+ R', k)
            if m:
                to_sort.append([int(m.group(1)), k, v])
    newobjectinfo = {x[1]: x[2] for x in sorted(to_sort)}
    if trailer is not None:
        newobjectinfo['trailer'] = trailer
    data['objectinfo'] = newobjectinfo
print(json_dumps(data))
----------

1 files changed, 7 insertions, 4 deletions

diff --git a/libqpdf/QPDFJob.cc b/libqpdf/QPDFJob.cc
index 63fa0c34..78c678b0 100644
--- a/libqpdf/QPDFJob.cc
+++ b/libqpdf/QPDFJob.cc
@@ -1066,13 +1066,14 @@ QPDFJob::doJSONObjects(Pipeline* p, bool& first, QPDF& pdf)
 void
 QPDFJob::doJSONObjectinfo(Pipeline* p, bool& first, QPDF& pdf)
 {
+    JSON::writeDictionaryKey(p, first, "objectinfo", 0);
+    bool first_object = true;
+    JSON::writeDictionaryOpen(p, first_object, 1);
     bool all_objects = m->json_objects.empty();
     std::set<QPDFObjGen> wanted_og = getWantedJSONObjects();
-    JSON j_objectinfo = JSON::makeDictionary();
     for (auto& obj: pdf.getAllObjects()) {
         if (all_objects || wanted_og.count(obj.getObjGen())) {
-            auto j_details = j_objectinfo.addDictionaryMember(
-                obj.unparse(), JSON::makeDictionary());
+            auto j_details = JSON::makeDictionary();
             auto j_stream =
                 j_details.addDictionaryMember("stream", JSON::makeDictionary());
             bool is_stream = obj.isStream();
@@ -1085,9 +1086,11 @@ QPDFJob::doJSONObjectinfo(Pipeline* p, bool& first, QPDF& pdf)
                 "filter",
                 (is_stream ? obj.getDict().getKey("/Filter").getJSON(true)
                            : JSON::makeNull()));
+            JSON::writeDictionaryItem(
+                p, first_object, obj.unparse(), j_details, 1);
         }
     }
-    JSON::writeDictionaryItem(p, first, "objectinfo", j_objectinfo, 0);
+    JSON::writeDictionaryClose(p, first_object, 1);
 }
 
 void